Long Article

PET/CT Calcium Scans: Higher Scores, Higher Risk

Wednesday, September 11, 2019

New research joins a growing chorus in favor of CAC screening to predict cardiac events — without upper thresholds.

Coronary artery calcium (CAC) scores performed by PET/CT scans give providers greater visibility into a patient’s individualized risk for a major cardiac event, according to new research presented at the American College of Cardiology’s 2019 meeting and reported by AuntMinnie.com.

The investigation, from Intermountain Medical Center Heart Institute in Salt Lake City, determined that the presence of calcification ticked up risk from a multidimensional perspective. Compared to patients without calcification, positive CAC scores led to elevated (and statistically significant) risks for having: a heart event within three months, coronary artery disease, and the need for revascularization within 48 months.1

Questions on upper limits

The research joins other clinical endorsements for CAC scoring, including that of the American Heart Association and American College of Cardiology — which in November 2018 released guidelines recommending CT CAC screening for patients at uncertain risk of atherosclerotic heart disease.2

But, coupled with new insights from JACC: Cardiovascular Imaging, the Salt Lake City research brings into question one major piece of those recommendations: upper thresholds for CAC scoring.

That’s because — according to the JACC research — the higher the CAC score, the higher a patient’s risk of a major cardiac event or all-cause mortality, with no cap limiting risk. Such caps have been considered, AuntMinnie.com reports, because of the mainstream belief that excessively high scores (well above 400 Agatston units, or AU) mark highly dense calcifications — such as “hearts of stone” seen in endurance athletes3 — rather than necessarily large, and therefore risky, ones.

The new research underscores the importance of PET/CT CAC scoring without upper limit considerations — with a particular emphasis on patients with CAC scores above 1,000 AU. For example, according to the JACC study and compared to those without calcifications, patients above 1,000 AU were…

…five times as likely to die from heart disease.

…three times as likely to die from any cause (including cancer).

Those patients also fared worse than patients whose scores fell between 400 and 999 AU:

Among those with CAC scores between 400 and 999 AU, 9.8 out of 1,000 people faced an all-cause risk of death.

Among those with CAC scores above 1,000 AU, 18.8 out of 1,000 people faced an all-cause risk of death.4

Contexts of CAC recommendations and applications

That evidence comes less than a year after a so-called “controversial”5 move from the U.S. Preventive Services Task Force, which gave CT CAC scoring an “I” grade when it indicated that more large-scale data was needed before calcium scores could be a viable route to indicating a patient’s individualized risk.6, 7

They went on to suggest that the scores could falsely inflate risk for patients who didn’t otherwise have any and trigger overuse of expensive medical testing and therapies, namely statins. But experts have countered, suggesting that CT CAC screening could actually do the opposite.

For example, the tool could help migrate patients from middle-risk categories into lower-rung ones for which no extra interventions beyond lifestyle modifications may be needed. In support of that argument, a February 2019 paper authored by AHA/ACC leaders and published in the Annals of Internal Medicine cited the scoring tool’s potential in preventing statin use among patients who don’t need them — such as those with a CAC score of zero.7

Other applications of PET/CT scans apply to scenarios in the emergency setting, so that providers can assess an angina patient’s likelihood of suffering a heart attack or other event with enough time to intervene.

Outside of those contexts, insights gleaned from CAC tests could help forecast down-the-road risk so that providers can offer impactful lifestyle adjustments to prevent adverse events altogether.1

Patient and provider benefits: outcomes, ease, and cost

As more research is born from these efforts, the growing chorus of CAC proponents stands to gain more traction from the cardiology community overall. As one provider from Cardiovascular Business put it, calcium scores are certainly not the “magic 8 ball” of risk prediction, but they’re a pretty good start.

The prospect of minimizing statin use for patients who don’t need them — while encouraging them for those who truly do — is a promising and cost-effective one. Add to that the potential to identify medication adherence through a real-time visual tool, and it’s quite clear that such a fast and non-invasive option, with minimal radiation exposure, is one that both patients and providers can rally around.